1. Field of the Invention
The present invention relates to a structure of a display device using a polarizer.
2. Description of the Related Art
A display device that is made to be extremely thin and lightweight as compared with the conventional cathode-ray tube, what is so-called, a flat panel display, has been developed. In the flat panel display, a liquid crystal display device including a liquid crystal element as a display element, a light emitting device including a self light emitting element, an FED (field emission display) utilizing an electron beam, and the like compete with each other. Therefore, as for the flat panel display, a low power consumption and a high contrast ratio are desired in order to enhance an added value and be differentiated from other products.
In a liquid crystal display device, each substrate is generally provided with one polarizing plate to keep the contrast ratio. The contrast ratio can be enhanced by further darkening black display much greater; accordingly, the liquid crystal display device can provide high display quality in a case where an image is seen in a dark room like a home theater.
In order to improve unevenness of display that is caused due to shortage of polarization degree and distribution of polarization degree of a polarizing plate and the contrast ratio, for example, a first polarizing plate is provided on an outer side of a substrate that is placed on a viewing side of a liquid crystal cell, and a second polarizing plate is provided on an outer side of a substrate that is placed on a side opposite to the viewing side. Then, light from an auxiliary light source that is provided on the substrate side opposite to the viewing side passes through the liquid crystal cell after being polarized through the second polarizing plate. In such a case, it is suggested that a third polarizing plate be provided in order to enhance polarization degree (refer to Patent Document 1: PCT International Publication No. 00/34821).